Process for the manufacture of polynuclear aromatic hydrocarbons



JllY 2 1.946- u. E. scHuLzE PROCESS'FOR THE MANUFACTURE OF POLYNUCLEAR AROMATIG HYDROCARBONS Filed Jan.' 7. 1942 Patented July 2, i946 PROCESS .FOR THE OF POLYNUCLEAR AROMATIC HYDROCAR BONS John E. Schulze, Chicago, lll.

Application January 7, 1942, Serial No. 425,842

This invention relates to processes for the purication of naphthalene, anthracene, phenanthrene, carbazol and other polynuclear aromatic hydrocarbons. The invention pertains particularly to the crystallizable `hydrocarbon constituents of coal tar belonging to the above mentioned class.

When crude coal tar (derived by destructive distillation of coal) is subjected to distillation, a number of condensates are obtained that contain various compounds of value as intermediates in the manufacture of dyestuffs, synthetic resins, medicinals and the like. While the specific treatment of any given coal tar may be governed by the nature of the tar being distilled, general results are probablysatisfactorily summarized in the following table:

Fraction collected Name of fraction Efercgltg 'Up to 170 C Light oil 0.2 l70230 C Carbolic oil (l/ phenol+% l0, 0

Y cresyllc acid).

Creosote oil 10. 0

50 25. 0 .Residue at 350 0.--.. Pit y 55.0

The carbolic and creosote `oil fractions representing about 20% of the crude coal tar are conventionally treated with causticsoda or the like for the removal of tar acids. The'remaining material contains minor proportions of neutral oils, aromatic'hydrocarbons, tar acids, pyridine bases, unsaturated hydrocarbons, sulfur containing compounds and other compounds together with major proportions of naphthalene in crystal form. Heretofore it has been found very diiilcult and costly to separate the above mentioned compounds from the'naphthalene so as to isolate pure naphthalene having a melting point of 80 C.

The residual material left after a caustic soda treatment of the carbolic and creosote oil fractions for the removal of tar acids is known to the trade as crude naphthalene. It has been a common practice -to press or centrifuge such crude naphthalene in order to separate the oils and other contaminants. ods fail to remove all the oil and other contaminants. For example, centrifuged crude naphthalene may have a melting point as low as 70 C. and may contain 20% or more of oil and other contaminants. This centrifuged material may be again centrifuged or even hot pressed to remove more oil and contaminants so as to raise its melting point to '14 or '78 C. but still con- 6 Claims. (Cl. 1260-674) tems impurities and is. som to the tradefasfcriid naphthalene. This material having a melting point of from '14 to 78 C. is tan-colored and has Y a tar-like odor. Y.

Another known method of purification com-r prises mixing crude naphthalene inzmolten condition with an aqueous alkaline medium, cooling the mixture to crystallize the crude naphthalene in the presence of ltheaqueous alkaline medium,

separating the liquid medium from1the naphy by centrifuging. 'I'his method yields a naphthalenehaving a melting point of from '78 to 78.5". C., which still has a d-arkcolor. To produce pure naphthalene havinga melting point of 80 C. from thusinc'ompletely purified naphthalene it is necessary to subject the latter material to further purification by.meltingtreating the molten naphthalene .rst with sulfuric acidl and then with a sodium hydroxidesolution and iinally distilling the treated material.

StillV another conventional methodof purifying crude naphthalene includes the steps of contactare not satisfactory, for the vpurified naphthaleneV obtained has a melting point ofonly '78 to 78.5 C., which indicates` that all the. contaminants have not been removed from the naphthalene.

'I'he above outlined and other conventional methods of manufacturing naphthalene by purication of coal tar fractions do not yield directly However, such methpure naphthalene having amelting point of C. Even when the purifying procedures are repeated or combined sok as finally to produce pure naphthalene, the final recovery or yield of `pure naphthalene is in all cases too low due to excessive naphthalene losses incurred by emulsication, chemical attack, inclusion with residues and like factors. The purification of naphthalene `by v conventional methods vis also expensiver because lene reducedv tojthe theoretical vf.Another;objectoftheinve t improved,purifying. fproc.edures.capable f `continuous.operationawhereby,greatereulcie cy and economy of operation maybejattai'n'ed.,,A

. ofthe necessarily large investment in equipment,

the consumption of large amounts of chemicals suchas sulfuric acid or sodium hydroxide, the

of kthe'purifying equipment, and like circuml stances. f

It is Vther'eferjeLian K important objectofnthi Y' l vention to provide a Vmethod of purifying naph-vv Vtlfllllle that does vnot entail the disadvantagesiclilloss of naphthalene and high ,costsrof ollll'ating` 1 i her nt'in conventional methods. of purifying A n e i *i* of the naphthalene 1nto the extract. If, on the crude naphthalene.

Another important object of the present inven tion is to provide an inexpensive and rapidmethod of producing directly from. crude naphthalene 1,. pure,l permanently colorless naphthalene'having 1 a melting point of 80 C.

A further object ofV thel inventionr is to Dlmlim.- ktion. eis ,to provide Vsun another objectief: the invention .retroprovideimproved purifying,. methods of '.the'nafture' l indicated thatarealso applicable to nuclear .arcmatichydrocarbons .than naphthaf lene,in..particularv` anthraclene, .phenanthrene carbazol and like materialspre's'entin vhigh boilinglocalizar-fractions)."'.; p I.

Otherand furtherobjectsand'f turesof-the ther' polyenifnno l the naphthalene. Y

. 4 Y solvent in its entirety below the boiling point of Solvents such as benzene, y tate, ethyl acetate, toluene and the like, if used. separately or in combination witheach other to wash .crude naphthalene would remove in their entirety all the impurities contained in the crude naphthalene.' However, v'such' solventagwhen employed at normal'working temperatures ranging `from 40 t0 100 would also have a high solvent power for naphthalene and if used at these presentinvention willbelc'ome apparent lfromthe followingdescription .and'appended claims.

. s outlined Ahereinabove by .Washing ,crude Nnaph wrefor naphthalene.

Such.washing is suitablyl The s4 lvent orv solvent mixture lbe ica rfriecllout atmormal4 workingV temperatures which may wary, say, from 402150 10,0.F.dependingon atmospherictem- 3 V'pe.ratujre's.l

1 liqui d1ali phatichydrocarbonhavingia .boiling f iontbeiowf thebolinjgrointf haphthelerleand Ywithwl'iich preferably is admixe'd. some .liquid 1 having a higher solventY ,ranging preferably 'bliWeDQ-"ane initial f v boiling excluding 'highl boiling solvents Il can be traced, to

Vpointofno'm 100 to 1509,11. and annarenqlpoint Vof' between 22,5% andV 275,.F. e 'Thenecessity of decreasing concentrationQaHence in. the case of .j

solvents which possess high boilingv points it be comes veryV dilcult to .remove the lasttraces of such osolventsfby. distillation,Y for. temperatures that approach or reach .the boiling point of naphtlfialene mustbe employed.Y In the case, however, of asolv'ent or solvent mixture having `an end l point-between225. and 275 F., all the solventi can be recovered ,at lowV operating temperatures without ventrainmentlof pure naphthalene, which hasatboning rangeof approximately 4.10a torno@y F. In' other words', vI am able to recover the temperatures would carry from 10 to 30% or more other hand, petroleum naphtha is used by itself amounts or traces of impuritiesV are left in the naphthalene.. Whether or not petroleum naphprovide a methodofepurifying crude naphthalene. includ-.

ingfnolchernical.treatment, whetherl.. acida sodium -hydroxide ,-,or other cherni cludi'ngfan extraction step requiring-m y 1 and no refrigerationwhile extraction of impuritiesis. effected; andinvolvinglossesof.naphthaf u tha per se is operative for complete purification attendees. I. have found. onine Ivre of, trade. n aphthalene being puried. Nowv I have found that petroleum naphtha has a relatively lowdegree of Solvent' power` for naphthalene, `the V solubilityw of naphthalene in., a petroleum fraction havingthey hereinabove specied boiling range being less than 2.5% at '70 to 80 F. By blending or mixing any ofthe hereinabove mentionedsolvente or their equivalents in the ratio of lfrom to 20%Y with Vfrom 80 to 95% of the petroleum fraction' I have obtained a combination solvent thatwill remove entirely all contaminants contained inY crude naphthalene with a minimum percentage of lost naphthalene in the` resulting extract. f Such combined solvents are also operative in the purification ofl such crudenaphthalene as can be satisfactorily puried leum naphtha. Y

More particularly, I may blend from to 95% of a petroleum fraction having a boiling range vfalling between an initial boiling point of F. and a final boiling point of,275' F. with from 5 to 20% acetone; or 80 to 95% of thev same petroleum fraction with from 5 to.20% benzene; vor

any other solvent mentioned hereinabove or any v'equivalentsolvent may be blended in the desired Yratio with a petroleum naphtha having a boiling range as set' forth, to form 'solvent blends having vthe specified boiling range'that can be utilized in the purification of crude naphthalene. Certeini additional advantages can be'obtained roy Y interblending several ofthe above mentioned solvents and blending in from 80 to 95% petroleum naphtha with from 5" to 20% of the resulting mixture.

It is important that the solvent'or solvent mix- `ture used should have great selectivity, i. e. ability to remove contaminants and deleterious comer the'v percentage of contaminating products con- 'tained therein. At the same time, the solvent or solvent mixture should be distinguished by low solvent power for naphthalene to render the percentage of recovery of this material high.

,In the case of a few types of crude naphthalene, 'petroleum naphtha is sufliciently vselective for complete purication with `good yield. In most cases, however, it is necessary, as indicated hereinabove. .to admix with the-petroleum naphtha or,the. like, minor proportions of organic liquids that are better solvents than petroleum naphtha acetone, methyl acenwith plain'retrfor naphthalene and, incidentally, the contaminants present in crude naphthalene. Such liquids include aromatic hydrocarbons, for instance, benzene; vketones such as acetone; esters such as methyl and ethyl acetates; alcohols such as methanolv and ethanol;y and other like solvents miscible with petroleum naphtha.

' The solvents and solvent mixtures used are such as are chemically inert toward the material treated. No naphthalene is lost or chemically modified by the solvents or solvent mixtures. Nor is there any corrosion'of the equipment used, which therefore may be made of ordinary construction materials. The' solvents or solvent mix.. tures are completely recoverable without the'use of any special fractionating means for the separation of solvent from extract and naphthalene by distillation. The solvents or solvent mixtures can be used at ordinary temperatures and are readily available commercially at a low cost;

The purifying process according to the present invention involves essentially a washing or extraction treatment of crude naphthalene or the like by means of the solvents or solvent mixtures disclosed hereinabove. It should be clearly understood that these liquid media, although referred to as solvents do not dissolve anything except the impurities to be removed and that very small amount of naphthalene which is carried away by the "solvents along with the contaminants. That naphthalene which is finally obtained in pure form remains in solid state during the whole washing or extracting process.

The working of the present invention is illustrated by the typical example of a specific method of purifying naphthalene according to the present invention described in some detail hereinbelow with special reference to the appendeddrawing showing diagrammatically a plantwherein the process of the invention can be eifectively carried out and including a flow sheet showing the progress of the various materials involved through the plant.

The drawing shows the principal apparatus or equipment parts in side elevation, with parts shown in longitudinal verticalY section. `The plant shown is adapted and arranged for the continuous processing of crude naphthalene stock having a melting point ranging all'the way from 55 C. to 78 C., to remove completely the `contaminating more or lesscomplex impurities varying inversely in amount according to the melting point of the material.

Liquid crude naphthalene having a melting'l point of 78"4 C. is drawn from astorage tank I0 throughs. supply line II by a pump' I2 and discharged through a line `I3 at the rate of 2.8 gallons or 231A, pounds per minute. The liquid crude naphthalene is discharged into the nip of a pair of opposed revolving cylinders I 4 internally cooled by water supplied by pipes I5. As soon as the liquid naphthalene contacts the cool surface of the rotating cylinders the liquid naphthalene crystallizes in the form of a thin sheet. 'I'he thickness of this sheet is governed by the spacing of the cylinders, which* are set to give sheets so thin as to be readily permeable by the washing medium after having been broken up. The

ycrystallized naphthalene in the rotating cylinders is shaped off by a knife edge (not shown), falling IBand thereafter enters a conveyor I9. The speed of the conveyor I9 is controlled to deliver 23%, pounds per minute to the counter-current extraction tower illv through the line 2I which extends down into the tower to a point distant from the top of the tower by about one foot. The extraction tower 20 may be 18 inches in diameter and 10 feet high, being constricted to a 12 inch diameter fora distance of about 5 feet from the base of the tower. A valve 22 located one foot from the bottom of the tower 20 is closed and re'- mains closed until the tower 20 has been rllledv with lcrude naphthalene.

When crushed crude naphthalene has reached the outlet level of the discharge line 2| in the tower, the conveyor I 9 is stopped. The -tower 20 has sight glasses (not shown) located at suitable points permitting visual inspection off the interior of the tower so that the level of naiph# thalene as well as the liquid level in the tower can be ascertained. When thus filled, the tower 20 will contain about 1250 Ypounds ofy crushed crude naphthalene. At the charging rate of 23% pounds per minute from the conveyor I9 it will take approximately 54 minutes to chargey the tower 20.

The' washing or extracting medium used may be a mixture o-f 5% acetone with 95% (by volume) of a petroleum naphtha fraction having an initial boiling point of 130 F. and a nal boiling point of 250 F. rIhis solvent mixture is now drawn from a storage tank 25 through aline it by a pump 27 and discharged through a line 28 to the tower 2i] ata controlled rate of 2.5 gallons per minute. This specific washingy medium has a specic gravity of 0.737 or 6.15 pounds per gallon, so that the total Weight of solvent fed to the tower per minute amounts to 15.37 pounds.

The outlet of the discharge line .28 into the tower -K 20 is located about 6 inches above the valve 22.

At the above mentioned controlled rate of solvent feed into the tower 20 approximately 60 minutes will elapse before the liquid level in the tower 20 will reach an overflow line 29. The crude naphthalene at the botto-m will then` have been washed byl all the solvent entering the tower and will be in substantially pure condition, the extracted impurities having been carried toward the top of the tower. At this time the solvent pump 2l is shut down and the valve 22 is opened. The purified naphthalene, compressed by the weight of overlying naphthalene and solvent so as to have all but 30% of its weight of solvent p squeezed out of the purified naphthalene, will into a hopper or container I 6 whence it falls into Crusher I'I where it is pulverized and crushed to a i'lneness such as to be readily permeable by the washing medium. The crushed crude naph- I thalene leaving the Crusher I 'I falls into a hopper leave the constricted base of the tower 20 and will enter a conveyor 30 which operates' against a pressure control valve or cone 3 I. The conveyor 30 is now started, and will discharge at a controlled rate of about 22 pounds per minute plus 30% by weight of clean extracting medium. At this time the conveyor I9 is again started,as is also the solvent feed pump 27, and the process is now ready for continuous operation. v

The extract together with the 70% (by weight of naphthalene) of spent solvent; displacing the same overflow through the outlet line 29 located at the top of the tower 20 through a line 32 to a pump 33 and are thence discharged through a line 34 to a heater 35. The last mentioned element may be a tubular typeheater. The heating medium can be either vsteam or hot circulating solventiisY recovered from Vcan be either steam or circulating hot oil.

the extract by atmosphericflash distillation. 1 The` solventvapor in the tower 31 is condensed in a final condenser 38. A- side'streamgfraction*nowsthrough a line 39to a pum'p 40, where also the distillate -from the condenser 38 is delivered through a pipe 4l. The pump 40 delivers the recovered solvent back to the Storage. tank 25' through a pipe line 42.

Y The extract left after solvent recovery from the distilling clumn131vis a residuerepresenting from'l'to 5% ofthe charge of crude naphthalene to the tower J2 0. This residue leaves the column 31 through a-line 45 and a pump 46, being discharged through a. line 41 to a storage tank (not shown). l

The. puried washed naphthalene containing about30% byweight of cleanl washing medium discharged from the conveyor 35 through the pressure valve 3| enters a closed tubular heater 50. The heating medium in this tubular heater In this heater the solvent processed or worked naphthalene is liquefied. The heating also brings this material up to the temperature required to distill oi the 30% solvent remaining in the processed naphthalene. For this purpose, the tubular heater 50 is formed as a closed vaporstage system and provided with a vapory dome 5l whence the vapors formed in the heater proper leave by way of a line 52 to enter an atmospheric distilling column 53. The liquid naphthalene toA gether with whatever solvent has not vaporized leaves the heater 50 through a line 54, entering a vpump 55 and beingv discharged through a line 5B intor the distilling column 53 for solvent recovery. Solvent vapor is condensed in the condenser 51 and ows through a line 58 and a pump 59 for discharge through a line 66 to the storage .tank 25.

The puried washed solvent-free liquid naphthalene left as a residue in the distilling column 53 has a good color and has a melting point of from '19.6 Vto '19.8 C. This residue represents from 95 to 96% of the crude naphthalene charged to tower 20. This liquid naphthalene leaves the tower 53 through a line 5|', being moved by ar pump 02 through a line 53, a tubular heater 64 anda pipe 55 into a vacuum distilling column 55 where the naphthalene is distilled at a reduced f pressure o n the order of from 50 to 75 millimeters of mercury (absolute pressure). The meansfor producing vacuum may comprise a steam jet 61. The temperature of distillation in the distilling colu-mn is approximately the'same as the temperature used for solvent recovery in the atmospheric distilling column 53 or, in other words, about 300 F. A low boiling naphthalene fraction amounting to 1% or less is recovered separately from a condenser 48 ahead of a baromet-- riecondenser 58, being discharged to storage through a line 69. This small low boiling naphthalene fraction apparently contains chemically unstable substances. 1

VThe main'portion of the naphthalene leaves nthe distilling column 66 through a side pipe'10,

flowing through a condenser 1I, a line 12, a pump 13 and a line 14 to storage.' 'I'his naphthalene fraction represents from 94 to 95% of the crude naphthalene entering the tower 20. This fraction is Water white in color, has a mild odor and a melting .point of 80 C. When subjected toa wash test, i. e. when a mixture of l1 cubic centimeters of chemically pure benzene, '1 cubic centimeters of melted naphthalene and 7 cubic centimeters of 9.5 to 98% chemically pure sulphuric Va line 11 to storage.

acidisshaken for. 5 seconds and allowed toV stand for v5 minutes,v the acid will have a color value of less than 5. Y

The residue from the tower 66 ilows through a line 15 to a pump 16 and is discharged through This residue represents about 1% of the crude naphthalene charged into the towerr20 andcan be accumulated and recycled separately or returned to the crude naphthalene storage. At least 95% of this residual 1% can be recovered as waterV white naphthalenehaving a melting point of C. The extract residue leaving the tower 31 can also be accumulated and lre-cycled. This vextract residue, which amounts to about 4 to.5% in the case offa crude naphthalene having a .melting point of 78 C.,- in turn has a melting point of 70 C, and is quite dark in color. When re-cyclingthis type of material it is necessary to use a solvent-solid ratio of. about 1% to l by Weight. By using such a solvent ratio I have'recovered from such ex-V tracted material 5.0% of its weight as pure naphthalene having a melting point of 80 C. 'I'he other half Vof the extract residue representing 21/2% of the crude naphthalene heated has a melting point of 63 C. and is very dark in color.

Thus, starting with crude naphthalene having a melting point of 18 C., the ultimate yield of Water white pure naphthalene having a melting point of 80 C. from the counter-current process described hereinabove will be as high as 97.5% whenusing the solvent and the solvent ratio de- Y scribed. The condensate leaving the tower 66 is Vthe naphthalene in liquid condition at all times.

Crude naphthalene having a melting point below 55 C. may advantageously be distilled fractionally before being purified by extraction asA disclosed'hereinabove. Thus, a. crude naphthalene having a melting point of 46 C. may be distilled, the' first 10% distilling over being discarded, and the next 60% being collected for A further purification. This 60% fraction contains substantially the whole naphthalene content of the crude product, having a, melting pointof 62 C. and a distillation range of from 380 and l 455 F. When puried by extraction according to the present invention, 42 out of the 60% may be Vrecovered as white naphthalene having a melting point of '19.6 C.

Extraction treatment according to this invention can be carried out by other than countercurrent means. For instance, a plurality of extraction towers may be charged with crude naphthalene and traversed successively by a current of extraction medium, the towers being cut out of the system in rotation for discharge of puri.-

ed naphthalene and recharging with crude naphthalene. l'

As shown by the illustrative `example described Y hereinabovathev present'invention provides a processv including a plurality of steps. The initial step includes comminuting naphthalene to make the same permeable to a liquid extraction medium. The second step comprises selectively exmedium containing impurities with clean" extraetion medium. The naphthalene subiectedvtole g traction may thenbe compressed, ,toexp' ess clean vextraction medium adhering thereto. UI)

- to this point the naphthalenek has beenltreate'd "in solid form' and at atmospheric' temperature; land. the impurities.' hav'ebeen removed fromthe naphthalene itself' and from. ,the extraction ine,- dium adheringfther'eto. Theextraction medium preferably contains petroleum naphtha boiling meer. ofierfedueiiee .ini-pertes eigener be rebetween 100 and 275 F., to which may be added aliphatic esters, alcohols and ketonesor aromatic hydrocarbons having a boiling range falling between 100 and 275 F., to increase the solvent power of the naphtha with'respect to the naphthalene impurities. The amounts of solvents added to the naphtha are minor fractions, in order not to raise the solvent power of the blend for naphthalene. When naphthalene containing relatively large amounts of impurities is purified, a product having the same melting point of from 79.6 to 79.8 C. as that obtained, say, from crude naphthalene melting at 78 C. may be obtained by increasing the ratio of extraction medium to naphthalene. If temperatures below 60 F. prevail during the extraction, it may also be advantageous to increase the extraction medium-naphthalene ratio, since at lower temperatures the naphthalene lparticles appear less permeable to the extraction medium or the latter lesseftlcient in removing impurities.

The third step includes heating the naphthalene subjected to extraction below its boiling point and above its melting point (if necessary) in order to expel extraction medium adhering thereto. The purified naphthalene thus obtained is of good color and may have a melting point of 79.6 to 79.8 C.

The fourth step, which is optional, includes a distillation of the naphthalene puriiied by extraction, the initial fraction of not more than one per cent being collected apart from the rest of the distillate, which consists of water white naphthalene having a melting point of 80 C., being chemically pure naphthalene suitable for any and all uses to which such naphthalene is put.

Naphthalene of a high degree of purity can thus be prepared without chemical action while keeping the naphthalene in solid state at atmospheric temperature. Naphthalene of various degrees of purity can be purified by the methods of this invention with excellent results. The only limitation imposed is that the crude naphthalene should not contain so great an amount of im purities as to be liquid when puried as outlined hereinabove.

Anthracene, phenanthrene, carbazol, mixtures thereof, and like materials can also be purified according to the present invention. Such materials are usually available in the form of crysstals having relatively high melting points, as compared with naphthalene, and need not be melted andthen solidified to be put into suitable form for extractive purification, although grindquired. i' t l. l.

A lvlanynietails.ofprockediire may bevari'ed within a wiaegraiige Witheet departing r *mm1 the prin.- eiplesqr, hisinventicn.rinitis therefore not my purps, "toiliinit the patent granted kon vlthis inventionotherwise, than necessitated bythe scope v of-theappended clailns. j Ifclaiin as my' invention l i .1l f method. f O DU' *gnaphthane irif .the mrninuting said naph- 'mnexfror-80-Jwr95frf of' petroleum; mapiitiiv having' 'a boiling ,fange falling bananen f an 275 4i?..togetlienvvith 'v Y Wierenl. te, fifdslllingiiore- -hei/.ine ii-5501111122; ferie@ teilige-'he'- endg/5' @ed eliafierfextretee impurities wel seid comminuted. naphthalene with a liquid medium containing from 'to 95% oi petroleum naphtha'having a .boiling rangey vralling between and 275 F. together with Y from 5 to 20% of an inert solvent for naphthalene capable of dissolving more than 2.5% naphe thalene and having a boiling range between 100 and 275 F., said extractiony being eifected by` solid state including comminuting said .naphtha-y lene to make the same permeable to a liquid extraction medium containing from 80 to 95% of petroleum naphtha having a boiling range falling between 100 and 275 F. together with'from 5 to 20% of an aliphatic alcohol having a boiling range falling between 100 and 275 F. and thereafterextracting impurities from said comminuted naphthalene with a liquid medium con' taining from 80 to 95% of petroleum naphtha having a boiling range falling between 100 and 275 F. .together'with from 5 to 20% `of an aliphatic alcohol having a boiling range between 100 and 275 F.

3:. A method orpurifying naphthalene in the solid statel including comminuting said naphthalene make the saine permeable to a liquid ex.- tracting medium containing from 80 to 95% of petroleum naphtha having a boiling range fallmg between 100 and 275 F. together with from 5 to 20% of an aliphatic ester having a boiling range .between 100 and 275 F. and thereafter extracting impurities from said comminuted naphthalene with a liquid medium containing from 80 to 95% of petroleum naphtha having a boiling range falling between 100 and 275 F. together with from 5 to 20% 4of an aliphatic ester Ilaving a boiling range of between 100 and 275 4. A method of purifying naphthalene in the solid State including comminuting said naphthalene to make the samepermeable to a liquid extracting medium containing from 80 to 95% of petroleum naphtha having'a boiling range' `falling between 100 and 275 F. together with from 5 to 20% of an aromatic hydrocarbon having a boiling range falling between 100 and 275 F. and thereafter extracting impurities from said comminuted naphthalene withv aliquid medium containing from 80 to 95% of petroleum naphtha having a boiling range falling between 100 and 275F. together with from 5 to 20% of an aroe vperr'neable lto a liquid` vi1 l Y Y itic'nydfocftn menge-heutigem@ @11mg between 100 and275 F. Y.

I "5. A1A method iof purifying naphthleiie `in the 'solid' state including 'Ycommin'uting sid' aphtha'- lenet make Ythe same permeable tela liqid jextl'actrig medium containingr from 80 tok `95% falling between 1009 and 275B F. together" with from 5 to 20% of ethylV acetate ndtheijfter "7%6; Thek method 0f ,purifying ciderraphtha-f ieneeentaining natnraylly'occrrin'g tgrfacidsnd other eontammjmmgV Vim @produce weie-from in a naphtnaiene-itoand/ through ndxt'raction .traetin zione ian extraction solvent comprieng at the 4advancing'n'aphixhalene priorv to being di'splaced lfrom jsaidextration kvzione with freslnhextiaction vSolvent, j 'oinpacting' said.` 'aphtha-le'ne to'ren'i/Qve therefreinj"a,*portionrv of said fresh ex fractions j.of Said apntngierie asf ne v10i" iit,'the tepsjnamed being :qarrie'd Vir-eer q'uentially as recited-and' as a eontiniioueipiece'ss.

'JOHN seni .y 

